Can I use the timeline to erase keyframes?
For 2.8 and newer:

This is now possible. Keys are shown as diamonds, like in the dope sheet. Mark them and hit X to delete them.

For 2.79 and earlier:

No; not in the timeline.
This is done in the Dope Sheet.


Hit B to select with a rectangle (or any other selection
method).
Hit X to delete selected keyframes.